This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Aer is receptor protein in E. coli that performs aerotaxis, that is it senses oxygen that modulates electron transport and proton motive force inside the cell. Unlike other receptors in this bacterium, Aer has a cytoplasmic PAS domain that binds FAD. We aim to explore the structure of this protein in detergents.